Shoe retracting mechanism



July 20, 1965 R. A. GOEPFRICH 3,195,638

SHOE RETRACTING MECHANISM 2 Sheets-Sheet 1 Original Filed Dec. 5. 1960 INVENTOR. RUDOLPH A. GOEPFRICH. EIE E BY 9 2 a y 2%, 1965 R. A GOEPFRICH 3,195,688

SHOE RETRACTING MECHANISM Original Filed Dec. 5, 1960 2 Sheets-Sheet 2 INVENTOR.

RUDOLBIJH A. GOEPFRICH. 9A a.

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United States Patent 3,195,688 SHGE RETRACTING MECHANISM Rudolph A. Goepfrich, Siouth Bend, Ind, assignor to The Bendix Corporation, Eiouth Bend, Ind., a corporation of Delaware Continuation of application Ser. No. 73,7?4, Dec. 5, 1950.

This application Sept. 20, 1962, Ser. No. 226,768 8 Claims. '{Cl. 18378) This application is a continuation-in-whole of copending application Serial No. 73,794, filed December 5, 1960, now abandoned. This invention relates to a shoe retracting mechanism and particularly, to a shoe retracting mechanism in a drum type brake wherein the shoes are expanded radially outwardly to engage the drum and retracted to a normally released position defined by engagement of the shoes with anchoring members.

In a complete brake assembly, it is necessary, that the brake shoes be supported axially as well as radially so that they are in position to engage the drum when they are actuated. Usually, this support is in the form of a backing plate having ledges on which the rims of the shoes take sliding support and extension fingers of the support plate which limit movement of the shoes in an axial direction away from the backing plate. By this means, the shoes are properly disposed in a lateral sense so that they are opposite the engagement surface of the drum. Additional locating means for the shoes, is generally in the form of anchoring members for the shoes which define the retracted position for the shoes and assist in supporting at least a portion of the weight of the shoes. To maintain the shoes in their normally retracted or released position, yieldable return spring means are fastened to the shoes to urge them to their retracted position. These spring forces can develop force components other than radial, and produce binding between the shoes and the lateral support so that the shoes tend to resist free radial movement; therefore, the shoes tend to remain in engagement with the drum causing a brake dragging condition even when the brake actuating forces are relieved.

Accordingly, it is one of the principal objects of the present invention to provide a novel shoe retracting means which develops retracting force on the shoes acting solely in a plane perpendicular to the cylindrical braking surface of the drum so that substantially no binding forces are effected between the shoe and its lateral support means tending to resist free retractile movement of the shoe. In this manner, brake dragging is substantially eliminated and the wear life of the brake is increased significantly.

Another object of the invention, is to provide a novel, structurally simple, brake-shoe-retracting mechanism which communicates retractile force on the shoes and is characterized by limiting such retractile force to forces acting in a brake retracting direction with substantially none of that force effective to create tipping forces on the shoes to hinder movement of the shoes away from their opposing engageable drum surface.

Another object of the invention is to provide simple and effective shoe-retracting means in the form of levers which communicate spring-developed retracting force to the brake shoes, said retracting means being readily secured to the backing plate.

Other objects and features of the invention will become apparent from a consideration of the following description which proceeds with reference to the accompanying drawings, wherein a plurality of embodiments of the invention are illustrated by way of example.

In the drawings:

FIGURE 1 is a plan view of a brake assembly having the retracting mechanism forming the subject of the present invention installed on the brake;

FIGURE 2 is a sectional View taken on line 2-2 of FIGURE 1;

FIGURE 3 is an enlarged detail view of the retaining means for holding the pivoted end of the retracting lever;

FIGURE 4 is a detail view of the retaining means but with the lever removed and looking in the direction of the arrows 4-4 in FIGURE 3;

FIGURE 5 is a sectional View taken on line 55 of FIGURE 2;

FIGURE 6 is an enlarged sectional view of another retaining means which is usable for attaching one end of the lever to the backing plate;

FIGURE 7 is a sectional view taken on line '7-7 of FIGURE 6;

FIGURE 8 is an enlarged detail view of a further embodiment of the invention showing another means of attaching the lever into the backing plate; and

FIGURE 9 is a sectional view taken on line 9-9 of FIGURE 8.

Referring now to the embodiment shown in FIGURES 1-5, and particularly to FIGURE 1, two identically constructed brake shoes 10 and 12 are each constructed of an arcuate rim 14 having friction material lining l6 and a transverse strengthening web 17. Between the two adjacent pairs of shoe ends there are hydraulic wheel cylinder actuators 18 and 20 each having oppositely acting pistons 22 and 24 acting through struts 26 and 2% to spread the ends of the shoes outwardly, thereby engaging the lining 1 .6 with the cylindrical surface 3d of a relatively rotatable drum 32. 1

Each shoe is anchored at one or the other of its ends on anchoring brackets 34 and 36, the anchoring of the shoe is dependent upon the direction of drum rotation during braking. Assuming for example that braking occurs with counterclockwise rotation of the drum as shown in FIGURE 1, the left hand end of shoe l0 and the right hand end of shoe 12 are the anchored ends.

- Each shoe is adjusted by means of an adjuster screw 35 which is interposed between one end of the shoe and its bracket. Each shoe is positioned laterally by means of ledges 38 and 40, formed integrally with backing plate 41, two such ledges being provided per brake shoe to locate the shoe laterally so that the lining 1-5 is parallel with the opposing drum surface 39. The edge of the rim id is in sliding engagement with its two ledges 38 and 4t and the side of each web 18 opposite the backing plate 41 engages a washer 42 which is secured to stem 4-4 by means of a nut 46. The shoe is thus held laterally between the washer 42 and ledges 38, 4%, these two means fixing the shoe laterally in its appropriate position. The two shoes are retained in a normally retracted position by means of return springs 4-3 and 5b which are fastened in tension between posts 52 secured to the anchors 34, 3-6 and levers 54, there being two levers and two return springs for each shoe to urge each end of the shoe toward its retracted position defined by engagement with anchors 34- and 36.

The springs 48 and 50 in previous brake structures exerted a tilting effect on the shoe tending to cause the shoe to rotate about an imaginary axis interconnecting the ends of the shoe. This tendency to rotate the shoe as described sometimes developed a binding elfect between the ledges 38, 4t and the washer 42 and thus prevented free retraction of the shoe whereby the lining 16 remained in engagement with the surface 30 of the drum thus causing dragging of the brake even when the actuator pressure was relieved. This dragging condition of the brakes detracts from the usable wear life of the lining 16, causes premature requirement for servicing of the brake, reduces efliciency of the vehicle by lowering gas mileage and causes overheating of the brake so that it is less efficient in operation.

In the present invention the return levers 54 develop all of their retractile force on the shoe within a plane which is perpendicular to the cylindrical surface 30 of the drum so that substantially none of the spring force tends to cause rotation of the shoes about an axis interconnecting the ends of the shoes. This will be clear from a consideration of the details of the construction of the levers 54. 7

Referring to FIGURE 2 each lever 54 has a rounded boss 56 which is received through an opening 58 in the shoe and forms a bearing surface therebetween. The one end 60 of the lever has a rounded boss 62 with a neck 64 bearing against a retainer 66 welded or otherwise suitably secured to backing plate 41 at 68. The retaining means 66 is in efiect a brace having a raised portion which provides a clearance between the raised portion and backing plate 41 and proportioned to receive the rounded boss 62 therein, the lever 54 being free to rotate or undergo pivotal movement about the end 60. Slot 69 in retaining means 66 is proportioned to receive neck 64 therein and the enlarged boss 62 cannot be picked out of the slot 69, thus insuring an adequate interlock between the retaining means 66 and lever end 60. Since the force of spring 48 tendsto rotate the lever 54 in a clockwise direction about bearing 56 (FIGURE 2) the end 60 of the lever is biased against the closed end of the slot 69 and thereby maintaining this position of engagement throughout the wear life of the brake,

The opposite end 70 of the lever 54 has two spaced enlargements 72 providing a groove therebetween suitable for receiving a hooking end 74 of spring 48.

All of the force of spring 48 on the brake shoe is resolved in a direction and location indicated by the arrow A I in FIGURE 2 and no lateral component is introduced by the force of spring 48 tending to raise the shoe away from the backing plate ledges into engagement with washer 42 or biasing it downwardly against the backing plate ledges; and, since there are no lateral forces tending to create a frictional effect between the washer 42 or ledges 38, 40 and either of the shoes, the shoes are free to slide without impedance on'their bearing surfaces with ledges 38, 40 and washer 42 thus alleviating dragging condition of the brakes. Because the spring force is always communicated to the brake shoe through bearing 56in socket 58 and since the lever 54 is free to pivot at its end 60, the spring 48 communicates its retracting force on the shoe solely in the plane of the web 17 of the brake shoe and continues to communicate such force at this location regardless of the adjustment of the shoes. In other Words, when the brake is first installed and the adjuster screws areturned inwardly to their maximum extent, the levers 54 tend to be tilted at a sharper angle and then tend to straighten to a perpendicular position relative to the shoe web 17 as the shoe is adjusted radially outwardly, Regardless of the angular disposition of the lever 54 i.e., its deviation from perpendicularity with the web 17, the spring force same as in the previous embodiments is received through a key-shaped opening 80 in the backing plate 41 and is retained by means of a cover plate 82 which has a keyshaped opening 84 with an enlarged section 86 proportioned to receive the boss 62 therethrough and a slot 88 which fits over neck 64 of the lever and thereby prevents movement of the lever 60 perpendicularly away from the backing plate 37 when the cover plate 82 is caused to slide into interlocking relation with the lever '60. The cover plate 82 substantially covers the opening 80 thus preventing entry of dirt, contaminant or the like within the interior of the brake, and since the cover is proportioned to be larger than the opening 80 it accomplishes its purpose of retaining the lever 60, permitting pivotal movement of the lever about end 60 and also covering opening tion have been described and selected for purposes of illustrating the invention, it will be understood that these are only examples of the invention and are in no sense restrictive thereof. It is reasonably to be expected that those skilled in the art can make numerous adaptations and revisions of the invention which suit individual design preferences It is intended that such revisions and variations of the invention as incorporate the herein disclosed principles will be included within the scope of the following claims as equivalents of the invention. i

I claim: 7

1. A drum brake comprising: a backing plate including support ledges, a pair of friction-material-lined arcuate T-section brake shoes slidably supported on said ledges and having adjacent ends, actuating means disposed be:

' tween each of said adjacent ends, anchoring means disposed between each of said adjacent ends, an opening in the webs of each of said shoes adjacent each end thereof, four levers each of which is transversely received through V a respective opening, each of said levers having a curved protuberance defining a bearing engaging the wall of its respective opening, said backing plate having retaining means receiving one lever end of each of said levers, said retaining means comprising an aperture for each of said one lever ends, each of said one lever ends comprising a round boss engaging the undersurfaceedge of its respecacting through the lever will continue to exert a force solely in the plane of the web of the shoe.

My invention contemplates other retainingmeans for the lever 54 which differ from the retaining means shown in FIGURES 2-4 and may include for example the one shown in FIGURES 6 and 7 wherein the end 60, of the lever is passed through an opening 76 of the, backing plate 37 and bears against one edge of the opening. The openingis formed oversize to allow for entry of the rounded boss 62 of the lever which is otherwise constructed the same as in the previous embodiment, To prevent entry of dirt or contaminants within the brake, the remainder of the opening 76 is filled with a rubber stopper 78 which fills the opening and extends around the neck 64 of the lever; Thelever is free to pivot within opening 76 just as it is free to pivot on retaining means 66 in the previous embodiment;

Referring next to the embodiment shown in FIGURES 8 and 9, the end of lever 54 which is constructed the tive aperture for pivotal movement thereat, each lever having a second lever end projecting from said shoe web in a direction away from said backing plate, and four re turn springs each of which is fastened in tension between a respective second lever end and a stationary part of the brake, whereby a retractile force is imparted through said bearings to said shoes urging each shoe to its retracted position defined by engagement with said anchoring means.

2. The structure as recited in claim 1 wherein each of said second lever ends has a groove therein receiving one end of its respective return spring.

3. The structure as recited in claim 1 wherein said aperture is in said backing plate. a

4. A brake having a rotatable drum, comprising: a backing plate, a pair of friction-material-lined T-section brake shoes slidably supported by said backing plate and having adjacent ends, actuating means disposed between at least one pair of said adjacent ends to effect outward movement engaging said shoes with said rotatable drum, anchoring means disposed between at least one pair of adjacent shoe ends to receive the anchoring load thereof, at least one opening in at least one shoe web, a lever transversely received through said opening of the shoe i5 projecting from said shoe Web in a direction away from said backing plate, and a return spring between said second lever end and a stationary part of said brake to impart retractile force to said shoe urging said shoe to'its retracted position defined by engagement with said anchoring means.

5. A brake having a rotatable drum, comprising: a backing plate, a pair of friction-material-lined T-section brake shoes slidably supported by said backing plate and having adjacent ends, actuating means disposed between at least one pair of adjacent ends to elfect outward movement engaging said shoes with said rotatable drum, anchoring means disposed between at least one pair of adjacent shoe ends to receive the anchoring load thereof, at least one opening in at least one shoe web, a lever transversely received through said opening of the shoe web, said backing plate having retaining means for receiving one lever end, said retaining means comprising an opening and intersecting slot in said backing plate, a rounded boss at said one lever end with an adjacent neck proportioned to fit through said opening and thereafter eltect locking by movement of said neck within said slot, sealing means for covering said backing plate opening, a second lever end projecting from said shoe web in a direction away from said backing plate, and a return spring between said second lever end and a stationary part of said brake to impart retractile force to said shoe urging said shoe to its retracted position defined by engagement with said anchoring means.

6. A brake having a rotatable drum, comprising: a backing plate, a pair of friction-material-lined T-section brake shoes slidably supported by said backing plate and having adjacent ends, actuating means disposed between at least one pair of said adjacent ends to elfect outward movement engaging said shoes with said rotatable drum, anchoring means disposed between at least one pair of adjacent shoe ends to receive the anchoring load thereof, at least one opening in at least one shoe web, a lever transversely received through said opening of the shoe web, said backing plate having retaining means for receiving one lever end, said one lever end comprising a rounded boss and a narrow neck adjacent thereto received through an opening of said backing plate, said retaining means comprising a fiat cover plate for said backing plate opening having an aperture proportioned to receive said boss therethrough and a slot slidably fitting over said neck to lock the one lever end with said backing plate and also provide pivotal lever movement about said one end, a second lever end projecting from said shoe web in a direction away from said backing plate, and a return spring between said second lever end and a stationary part of said brake to impart retractile force to said shoe urging said shoe to its retracted position defined by engagement with said anchoring means.

7. A brake having a rotatable drum, comprising: a backing plate, a pair of friction-material-lined T-section brake shoes slidably supported by said backing plate and having adajcent ends, actuating means disposed between at least one pair of said adjacent ends to effect outward movement engaging said shoes with said rotatable drum, anchoring means disposed between at least one pair of adjacent shoe ends to receivethe anchoring load thereof, at least one opening in at least one shoe web, a lever transversely received through said opening of the shoe web, said backing plate having retaining means for receiving one lever end, said retaining means comprising a brace having a slot in a portion thereof raised from said backing plate, a rounded boss at said one lever end received between said backing plate and raised portion, and a neck adjacent said boss and received within said slot to interlock said one lever end and brace but provide pivotal movement therebetween, a second lever end projecting from said shoe web in a direction away from said backing plate, and a return spring between said second lever end and a stationary part of said brake to impart retractile force to said shoe urging said shoe to its retracted position defined by engagement with said anchoring means.

8. The brake structure in accordance with claim 1 wherein said retaining means comprises a brace having a slot in a portion thereof raised from said backing plate, a rounded boss at said one lever end received between said backing plate and raised portion, and a neck adjacent said boss and received within said slot to interlock said one lever end and brace but provide pivotal movement thereat.

References Cited by the Examiner UNITED STATES PATENTS 1,948,822 2/34 Lindblorn 188-78 2,095,753 10/37 La Brie 188-795 2,251,854 8/41 Parnell et al 188-78 2,557,820 6/51 Frank 188-78 2,822,065 2/58 Goepfrich et a1 188-152 2,976,958 3/61 Scholl 188-79 3,061,051 10/62 Swift 188-78 EUGENE G. BOTZ, Primary Examiner. ARTHUR LA POINT, MILTON BUCHLER, Examiners. 

1. A DRUM BRAKE COMPRISING: A BACKING PLATE INCLUDING SUPPORT LEDGES, A PAIR OF FRICTION-MATERIAL-LINED ARCUATE T-SECTION BRAKE SHOES SLIDABLY SUPPORTED ON SAID LEDGES AND HAVING ADJACENT ENDS, ACTUATING MEANS DISPOSED BETWEEN EACH OF SAID ADJACENT ENDS, ANCHORING MEANS DISPOSED BETWEEN EACH OF SAID ADJACENT ENDS, AN OPENING IN THE WEBS OF EACH OF SAID SHOES ADJACENT EADN END THEREOF, FOUR LEVERS EACH OF WHICH IS TRANSVERSELY RECEIVED THROUGH A RESPECTIVE OPENING, EACH OF SAID LEVERS HAVING A CURVED PROTUBERANCE DEFINIG A BEARING ENGAGING THE WALL OF ITS RESPECTIVE OPENING, SAID BACKING PLATE HAVING RETAINING MEANS RECEIVING ONE LEVER END OF EACH OF SAID LEVERS, SAID RETAINING MEANS COMPRISING AN APERTURE FOR EACH OF SAID ONE LEVER ENDS, EACH OF SAID ONE LEVER ENDS COMPRISING A ROUND BOSS ENGAGING THE UNDERSURFACE EDGE OF ITS RESPECTIVE APERTURE FOR PIVOTAL MOVEMENT THERAT, EACH LEVER HAVING A SECOND LEVER END PROJECTING FROM SAID SHOE WEB IN A DIRECTION AWAY FROM SAID BACKING PLATE, AND FOUR RETURN SPRINGS EACH OF WHICH IS FASTENED IN TENSION BETWEEN A RESPECTIVE SECOND LEVER END AND A STATIONARY PART OF THE BRAKE, WHEREBY A RETRACTILE FORCE IS IMPARTED THROUGH SAID BEARINGS TO SAID SHOES URGING EACH SHOE TO ITS RETRACTED POSITION DEFINED BY ENGAGEMENT WITH SAID ANCHORING MEANS. 